[FFmpeg-user] Chroma subsampling formats

[Jim DeLaHunt]

On 2025-07-18 07:47, Mark Filipak wrote:

> ...I want to give
> folks the opportunity to correct what I've written and to make additions....

OK, I'll bite.

In trying to follow along with this thread, i have had two difficulties:

1. not explaining the notation.

It's great that your message of Fri, 18 Jul 2025 10:47:01 -0400 has a 
Key. That is a good start to explaining notation. But note that the 
first symbol you use is "¤", which is not in your Key.

Also, you use terms like 4:2:2 and 4:1:1, without citing which notation 
system you are using. I observe that the Wikipedia article on Chroma 
subsampling mentions "schemes are not expressible in J:a:b notation. 
Instead, they adopt a Y:Cb:Cr notation". Both notations look 
syntactically identical. Which do you mean?  When talking to an expert 
like Poynton, maybe this all goes without saying. But when trying to 
understand fundamentals, maybe it helps to be extra clear.

2. limiting yourself to character graphics.

You are attempting to communicate about two-dimensional arrays of 
samples and loci. 2-D line graphics are a much clearer way of expressing 
those concepts than are character graphics. I suspect that limiting 
yourself to character graphics will limit your ability to express 
clearly what you are trying to say about two-dimensional concepts.

Yes, making a line drawing is harder than making a character graphics 
diagram. It requires using a different tool than a text editor, for a 
start. But if you want to communicate clearly, maybe it is required.

Now I am not an expert, so maybe my difficulties won't apply between you 
and Poynton. But this is my addition.

Best regards,
      —Jim DeLaHunt